Additional sampling directions improve detection range of wireless RF probes
Additional sampling directions improve detection range of wireless probes
Magnetic Resonance in Medicine
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Hoffmann, M., Mada, M., Carpenter, A., Sawiak, S., & Williams, G. (2015). Additional sampling directions improve detection range of wireless RF probes. Magnetic Resonance in Medicine https://doi.org/10.1002/mrm.25993
Purpose: While MRI is enhancing our knowledge about the structure and function of the human brain, subject motion remains a problem in many clinical applications. Recently, the use of wireless radio-frequency markers with three 1D navigators for prospective correction was demonstrated. This method is restricted in the range of motion that can be corrected, however, because of limited information in the 1D readouts. Methods: Here, the limitation of techniques for disambiguating marker locations was investigated. It was shown that including more sampling directions extends the tracking range for head rotations. The efficiency of trading readout resolution for speed was explored. Results: Tracking of head rotations was demonstrated from -19.2 to 34.4°, -2.7 to 10.0° and -60.9 to 70.9° in the x-, y- and z-directions respectively. In the presence of excessive head motion, the deviation of marker estimates from SPM8 was reduced by 17.1% over existing three-projection methods. This was achieved by using an additional seven directions, extending the time needed for readouts by a factor of 3.3. Much of this increase may be circumvented by reducing resolution, without compromising accuracy. Conclusion: Including additional sampling directions extends the range in which markers can be used, for patients who move a lot.
Wireless RF markers, head motion, prospective correction
The project was supported by funding from the Isaac Newton Trust, the Wellcome Trust ISSF, and the Cusanuswerk funding body (Bonn, Germany).
External DOI: https://doi.org/10.1002/mrm.25993
This record's URL: https://www.repository.cam.ac.uk/handle/1810/250453
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Licence URL: http://creativecommons.org/licenses/by/4.0/